Gaseous emissions treatment components and methods for manufacturing thereof

ABSTRACT

A gaseous emissions treatment component is made by extruding a green ceramic mix through a die to form an extrusion having a honeycomb substrate with elongate cells extending its length and with the cells bounded by walls dividing adjacent cells from one another. Molten metal for use in induction heating of the component is placed in selected cells and is solidified by cooling.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. patent application is a continuation-in-partapplication of U.S. patent application Ser. No. 15/650,416 filed Jul.14, 2017 and entitled “A catalytic converter component and process forits manufacture”, which is a continuation application of U.S. patentapplication Ser. No. 13/971,247 filed Aug. 20, 2013 entitled “Processfor manufacturing a component for a catalytic converter” now issued asU.S. Pat. No. 9,737,851, which claims priority pursuant to 35 U.S.C.119(e) to U.S. Provisional Patent Application 61/692,732 entitled “Acatalytic converter component and process for its manufacture,” filedAug. 24, 2012 and U.S. Provisional Application 61/733,949, entitled “Acatalytic converter component and process for its manufacture,” filedDec. 6, 2012.

The present U.S. patent application is a continuation-in-partapplication of U.S. patent application Ser. No. 15/259,858 filed Sep. 8,2016 and entitled “Gaseous emissions treatment structures with inductionheating”, which is a continuation application of U.S. patent applicationSer. No. 14/452,800 filed Aug. 6, 2014 entitled “Catalytic converterstructures with induction heating” now issued as U.S. Pat. No.9,488,085, which claims priority pursuant to 35 U.S.C. 119(e) from U.S.Provisional Application 61/879,211 entitled “Catalytic converteremploying electrohydrodynamic technology” filed Sep. 18, 2013 and U.S.Provisional Patent Application 61/910,067 entitled “Catalytic converterusing field heating of metal component” filed Nov. 28, 2013.

All of the above-mentioned applications are hereby incorporated hereinby reference in their entirety and made part of the present U.S. patentapplication for all purposes.

FIELD OF THE INVENTION

This invention relates to gaseous emissions treatment components andmethods for manufacturing thereof, such components having particular butnot exclusive application to catalytic converters, particulate filters(PFs) and like structures for treating exhaust gases to reduce harmfulpollution.

BACKGROUND

The U.S. Department of Transportation (DOT) and the U.S. EnvironmentalProtection Agency (EPA) have established U.S. federal rules that setnational greenhouse gas emission standards. Beginning with 2012 modelyear vehicles, automobile manufacturers required that fleet-widegreenhouse gas emissions be reduced by approximately five percent everyyear. Included in the requirements, for example, the new standardsdecreed that new passenger cars, light-duty trucks, and medium-dutypassenger vehicles had to have an estimated combined average emissionslevel no greater than 250 grams of carbon dioxide (CO₂) per mile invehicle model year 2016.

Catalytic converters and DPFs are used in internal combustion engines toreduce noxious exhaust emissions arising when fuel is burned as part ofthe combustion cycle. Significant among such emissions are carbonmonoxide and nitric oxide. These gases are dangerous to health but canbe converted to less noxious gases by oxidation respectively to carbondioxide and nitrogen/oxygen. Other noxious gaseous emission products,including unburned hydrocarbons, can also be converted either byoxidation or reduction to less noxious forms. The conversion processescan be effected or accelerated if they are performed at high temperatureand in the presence of a suitable catalyst being matched to theparticular noxious emission gas that is to be processed and converted toa benign gaseous form. For example, typical catalysts for the conversionof carbon monoxide to carbon dioxide are finely divided platinum andpalladium, while a typical catalyst for the conversion of nitric oxideto nitrogen and oxygen is finely divided rhodium.

Catalytic converters and PFs have low efficiency when cold, i.e. therunning temperature from ambient air start-up temperature to atemperature of the order typically of 300 C or “light-off” temperature,being the temperature where the metal catalyst starts to accelerate thepollutant conversion processes previously described. Light-off is oftencharacterized as the temperature at which a 50% reduction in toxicemissions occurs and for gasoline is approximately 300° C. Belowlight-off temperature, little to no catalytic action takes place. Thisis therefore the period during a vehicle's daily use during which mostof the vehicle's polluting emissions are produced. Getting the catalyticconverter or PF hot as quickly as possible is important to reducing coldstart emissions.

U.S. patent application Ser. No. 14/452,800 (Catalytic converterstructures with induction heating) shows a catalytic converter assemblyhaving a substrate body with a plurality of cells for passagetherethrough of exhaust gases. Metal is located at predeterminedlocations in the substrate body and an electromagnetic field generatoris mounted adjacent the substrate body for generating a varyingelectromagnetic field inductively to heat the metal and so heat thesubstrate body.

SUMMARY OF THE INVENTION

According to one aspect of the invention, there is provided a method ofmaking a gaseous emissions treatment component, comprising extrudinggreen ceramic mix through a die to form an extrusion having a honeycombsubstrate having a plurality of elongate cells extending along theextrusion, the cells bounded by walls dividing adjacent cells from oneanother, cutting off a length of the extrusion, placing molten metal foruse in induction heating of the component in at least a part of at leastsome of the cells in said length, and solidifying the molten metal bycooling. Preferably, a catalyst metal washcoat is applied to walls ofopen cells of the substrate after placing said molten metal in said atleast some of the cells.

Preferably the honeycomb substrate is fired before the molten metal isplaced. In one variation, at least some of the cells are at leastpartially filled such that the molten metal, on solidification, formsblocking plugs in said cells. The molten metal can be injected at highpressure into unheated cells. In one form, the at least some of thecells are at least partially filled with molten metal such that themolten metal is a layer on the walls of said cells. In one variation,the honeycomb substrate is heated prior to placing molten metal in saidat least a part of said at least some of the cells. In one form, theheating is such as to heat the substrate to a temperature close to butbelow the melting temperature of the metal. The metal can be initiallyintroduced in solid form into said at least some cells, with theintroduced metal then being heated to melt the introduced metal wherebyit becomes the placed metal. In one form, the introduced metal in solidform is particulate metal in a fluidized flow with a reservoircontaining the particles being conditioned for fluidized flow by one ofvibrating a vessel containing the reservoir of particles and injectingair into a vessel containing the reservoir of particles. In anotherform, the introduced metal in solid form is a metal wire.

Preferably, said cooling acts to cool and solidify the molten metal tocause first shrinkage of the metal and acts to cool the substrate tocause second shrinkage of the substrate less than the first shrinkage,whereby at solidification of the metal, a space is established at atleast some of the interface between the solidified metal and adjacentwalls of said at least some of the cells. Preferably, the nature of themetal, the nature of the substrate material and dimensions of the atleast some of the cells are selected such that when the component isbeing used in emissions treatment and an operating temperature of thecomponent increases from an expected lowest temperature operation to anexpected highest temperature operation, differential expansion betweenthe metal and the substrate does not fully close said space. Typically,a road vehicle gasoline engine might expect to be operated at atemperature reaching minus 80 degrees C. at start up in a very coldregion to a temperature of 1000 degrees C. for highway driving. In oneform, the walls of the at least some of the cells are provided withtextured surfaces during formation of the extrusion whereby the moltenmetal, as it solidifies, acquires, to some extent, a matching texture.

According to another aspect of the invention, there is provided a methodof making a gaseous emissions treatment component, comprising extrudinggreen ceramic mix through a die to form an extrusion having a pluralityof elongate cells extending along the extrusion, the cells bounded bywalls dividing adjacent cells from one another, cutting off and firing alength of the extrusion to form a honeycomb substrate, placing slurrycontaining particles of a metal for use in induction heating of thecomponent in at least some of the cells of the substrate, and firing theslurry coating to bond the coating to the walls and to consolidate themetal particles. Preferably, a washcoat of catalyst metal for use ingaseous emissions treatment is applied over the layer of fired slurry.Preferably, the slurry contains particles of a catalyst metal for use ingaseous emissions treatment. Preferably, said placing slurry comprisingforcing slurry into said at least some cells, and drying the slurry toform plugs.

According to a further aspect of the invention, there is provided amethod of making a gaseous emissions treatment component, comprisingextruding ceramic mix through a die to form an extrusion having aplurality of elongate cells extending along the extrusion, the cellsbounded by walls dividing adjacent cells from one another, in concertwith the extruding feeding metal through the die with the extruded mix,and cutting off and firing a length of the extrusion and associatedmetal to form a honeycomb substrate. The metal can comprise metal wireswith the wire being fed through apertures in the die at the sites ofsaid at least some of the cells. Preferably, the apertures closely matchthe cross-sectional shape and size of the wires. Alternatively the metalwires are entrained in the walls of the extrusion as the ceramic mix isextruded through the die. In both cases, forward ends of the wires canbe fixed to a pull fixture with the pull fixture being pulled tomaintain the wires in tension and in desired positions in the extrudate.In a further alternative, the metal can comprise metal particles mixedwith the green ceramic mix with the feeding of the metal particles beingthrough apertures in the die at the sites of said at least some of thecells. Preferably, the firing acts to bond the metal particles andceramic mix to the walls. Preferably, the concentration of the metalparticles is made sufficiently high that, upon firing, at least some ofthe metal particles consolidate as a metal mass.

According to another aspect of the invention, there is provided a methodof making a gaseous emissions treatment component, comprising extrudinggreen ceramic mix through a die to form an extrusion having a pluralityof elongate cells extending along the extrusion, the cells bounded bywalls dividing adjacent cells from one another, cutting off and firing alength of the extrusion to form a honeycomb substrate, and depositing alayer of metal on inside surfaces of the cells by electrolysis.Preferably, a conducting layer is applied to the inside surfaces priorto the electrolytic deposition, the application being by one of dippingthe substrate in molten metal salts and painting with metalized paint.

According to a further aspect of the invention, there is provided amethod of making a gaseous emissions treatment component, comprisingextruding green ceramic mix through a die to form an extrusion having aplurality of elongate cells extending along the extrusion, the cellsbounded by walls dividing adjacent cells from one another, cutting offand firing a length of the extrusion to form a honeycomb substrate, anddepositing a layer of atomized molten metal on inside surfaces of atleast some of the cells by plasma spraying. The atomized molten metalcan generated by directing metal powder through a flame and intoentrances of the selected cells. Alternatively, the atomized moltenmetal is generated by rendering the metal molten, feeding molten metalto a spray head and spraying molten metal into entrances of the selectedcells. In each case, either or both of the substrate and theatomizer/spray head is moved through a locus in which coupled withgravity, metal is caused to deposit at locations along the cells spacedfrom the entrances thereof. In particular, the substrate is the atomizedmolten metal is directed from one end of the substrate and then isdirected from the other end of the substrate. Preferably, vacuum and/orblow assist is used to improve profile of the deposited layer.

BRIEF DESCRIPTION OF THE DRAWING

For simplicity and clarity of illustration, elements illustrated in theaccompanying figure are not drawn to common scale. For example, thedimensions of some of the elements are exaggerated relative to otherelements for clarity. Advantages, features and characteristics of thepresent invention, as well as methods, operation and functions ofrelated elements of structure, and the combinations of parts andeconomies of manufacture, will become apparent upon consideration of thefollowing description and claims with reference to the accompanyingdrawings, all of which form a part of the specification, wherein likereference numerals designate corresponding parts in the various figures,and wherein:

For simplicity and clarity of illustration, elements illustrated in theaccompanying figure are not drawn to common scale. For example, thedimensions of some of the elements are exaggerated relative to otherelements for clarity. Advantages, features and characteristics of thepresent invention, as well as methods, operation and functions ofrelated elements of structure, and the combinations of parts andeconomies of manufacture, will become apparent upon consideration of thefollowing description and claims with reference to the accompanyingdrawings, all of which form a part of the specification, wherein likereference numerals designate corresponding parts in the various figures,and wherein:

FIG. 1 is a longitudinal sectional view of a prior art gaseous emissionstreatment unit.

FIG. 2 is a longitudinal sectional view of a gaseous emissions treatmentunit adapted for use in an embodiment of the invention.

FIG. 3 is a cross-sectional view of the unit of FIG. 2.

FIG. 4 is a perspective sectional view of a part of a gaseous emissionstreatment unit according to an embodiment of the invention showing metalinserts located in cells of a substrate body.

FIG. 5 is a detail view of part of apparatus being used in a method forinjecting molten metal into cells of a ceramic substrate according toone embodiment of the invention for use in making a component for agaseous emissions treatment system.

FIG. 6 is a detail view of part of apparatus being used in analternative method for injecting molten metal into cells of a ceramicsubstrate according to one embodiment of the invention for use in makinga component for a gaseous emissions treatment system.

FIG. 7 is a detail view of part of apparatus being used to apply acatalyst layer to cell walls of the ceramic substrate of FIG. 6.

FIG. 8 is a detail view of part of apparatus being used in a method forplacing metal particles into cells of a ceramic substrate according toone embodiment of the invention for use in making a component for agaseous emissions treatment system.

FIG. 9 is a detail view of part of apparatus being used in analternative method for placing metal particles into cells of a ceramicsubstrate using fluidized flow according to one embodiment of theinvention for use in making a component for a gaseous emissionstreatment system.

FIG. 10 is a detail view of part of apparatus being used in a method forplacing metal particles into cells of a ceramic substrate, the metalbeing initially contained in a slurry, the method according to oneembodiment of the invention for use in making a component for a gaseousemissions treatment system.

FIG. 11 is a detail view of part of apparatus being used to establishmetal placed inside cells of a ceramic substrate a spacing between theoutside surface of the metal and the inside surface of the cells, themethod according to one embodiment of the invention for use in making acomponent for a gaseous emissions treatment system.

FIG. 12 is a detail view of part of apparatus being used in a method forpulling wires through a die in concert with extruding clay orclay/ceramic mix through the die to produce an extrusion containing thewires, the method according to one embodiment of the invention for usein making a component for a gaseous emissions treatment system.

FIG. 13 is a detail view of part of apparatus being used in a method forco-extruding particulate metal and clay or clay/ceramic mix through thedie to produce an extrusion containing the particulate metal, the methodaccording to an embodiment of the invention for use in making acomponent for a gaseous emissions treatment system.

FIG. 14A is a detail view of part of apparatus being used in a methodfor generating atomized metal from metal powder and for depositing theatomized metal on inside surfaces of cells of a ceramic substrate, themethod according to an embodiment of the invention for use in making acomponent for a gaseous emissions treatment system.

FIG. 14B is a detail view of part of apparatus being used in a methodfor generating atomized metal from reservoir of molten metal and fordepositing the atomized metal on inside surfaces of cells of a ceramicsubstrate, the method according to an embodiment of the invention foruse in making a component for a gaseous emissions treatment system.

FIGS. 15 and 16 are detail views of part of apparatus being used in amethod for depositing metal on inside surfaces of cells of a ceramicsubstrate by means of electrolysis, the method according to anembodiment of the invention for use in making a component for a gaseousemissions treatment system.

DETAILED DESCRIPTION OF THE INVENTION INCLUDING THE PRESENTLY PREFERREDEMBODIMENTS

A gaseous emissions treatment assembly may take any of a number offorms. Typical of these is a catalytic converter having a cylindricalsubstrate body 10 usually made of ceramic material and often called abrick, an example of which is shown in FIG. 1. The brick has a honeycombstructure in which a number of small area passages or cells 12 extendthe length of the brick, the cells being separated by walls 14. Thereare typically from 400 to 900 cells per square inch (cpsi) ofcross-sectional area of the substrate body 10 and the walls aretypically in the range 0.003 to 0.008 inches in thickness. Typically,the ceramic substrate body 10 is formed in an extrusion process in whichgreen ceramic material—containing clay or a mix of clay and particulateceramic—is extruded through an appropriately shaped die and units arecut successively from the extrusion. The units are fired to convert theclay component to ceramic, the units being then cut into bricks. Theareal shape of the cells or passages 12 may be whatever is convenientfor contributing to the overall strength of the substrate body 10 whilepresenting a large contact area at which flowing exhaust gases caninteract with a hot catalyst coating the interior walls of the cells. Inother gaseous emissions treatment such as particulate filters, there mayor may not be catalyst coating on the passage walls. In particulatefilters, a checkerboard subset of cells have their front ends plugged, a‘reverse’ checkerboard subset of cells have their back ends plugged, andgaseous emissions are treated by being driven though porous walls of thehoneycomb structure from cells of the first subset into cells of thereverse subset.

In the catalytic converter, interiors of the tubular cells 12 arewash-coated with a layer containing a particular catalyst material. Awash-coat typically contains a base material, suitable for ensuringadherence to the cured ceramic material of the substrate body, andentrained particulate catalyst material for promoting specificpollution-reducing chemical reactions. Examples of such catalystmaterials are platinum and palladium which are catalysts effective inconverting carbon monoxide and oxygen to carbon dioxide, and rhodiumwhich is a catalyst suitable for converting nitric oxide to nitrogen andoxygen. Other catalysts are known which promote high temperatureoxidation or reduction of other gaseous materials. The wash-coating isprepared by generating a suspension of the finely divided catalyst in aceramic paste or slurry, the ceramic slurry serving to cause thewash-coat layer to adhere to the walls of the ceramic substrate body. Asan alternative to wash-coating to place catalyst materials on thesubstrate body surfaces, the substrate body material itself may containa catalyst so that the brick presents catalyst material at the internalsurfaces bounding the cells.

Exhaust gases from diesel (compression combustion) engines contain morenitrogen oxides than gasoline (spark combustion) engines. Long-termexposure to nitrogen oxides even at low levels can cause temporary orpermanent respiratory problems. Selective catalytic reduction (SCR) is amethod by which a liquid reductant is injected into a diesel engineexhaust flow to combine with nitrogen dioxide and nitric oxide (referredto collectively as NO_(X)) in the exhaust gas. A preferred reductant isaqueous urea (2(NH₂)₂CO which is often referred to as diesel exhaustfluid (DEF). In the presence of a catalyst, ammonia resulting fromthermal decomposition of the urea combines with the nitrogen oxides toproduce less harmful products, chiefly nitrogen and water. Otherreductants such as anhydrous ammonia and aqueous ammonia may also beused as an alternative to urea although especially for automotiveapplication, on-board storage presents greater difficulty. Suitablecatalysts may be any of certain metals oxides (such as those ofmolybdenum, vanadium, and tungsten), certain precious metals andzeolites. The typical temperature range for a SCR reaction is from 360°C. to 450° C. with a catalyst such as activated carbon being used tostimulate lower temperature reactions. As in gasoline (spark combustionengines), diesel (pressure combustion) engines may experience a periodafter a start-up where the exhaust temperature is too cool for effectiveSCR NO_(x) reduction processes to take place. Other catalytic convertersin which the present invention finds application for preheating orsupplementary heating are lean NOX catalyst systems, lean NOX trapsystems and non-selective catalytic reduction systems. The presentinvention is applicable also to each of these nitrogen oxide emissionstreatment assemblies.

A gaseous emissions treatment assembly may have a series of thesubstrate bodies or bricks 10, each having a particular catalyst layeror emissions treatment mode depending on the noxious emission to bereduced or neutralized. Gaseous emissions treatment bricks may be madeof materials other than fired ceramic, such as stainless steel. Also,they may have different forms of honeycombed cells or passages thanthose described above. For example, cells can be round, square,hexagonal, triangular or other convenient cross-sectional shape. Inaddition, if desired for optimizing strength and low thermal capacity orfor other purposes, some of the extruded honeycomb walls can be formedso as to be thicker than other of the walls or formed so that there issome variety in the shape and size of cells. Junctions between adjacentinterior cell walls can be sharp angled or can present curved profiles.

Typically, as shown in FIG. 1, the wash-coated ceramic honeycomb brick10 is wrapped in a ceramic fibrous expansion blanket 16. A sheet metalcasing or can 18 transitions between the parts of an exhaust pipe (notshown) fore and aft of the gaseous emissions treatment component so asto encompass the blanket wrapped brick. The casing 18 is typically madeup of two parts which are welded to seal the brick in place. Theexpansion blanket 16 provides a buffer between the casing 18 and thebrick 10 to accommodate their dissimilar thermal expansion coefficients.The metal of the sheet metal casing 18 expands much more than theceramic material of the brick at a given temperature increase and, ifthe two materials were bonded together or in direct contact with eachother, destructive stresses would be experienced at the interface of thetwo materials. The blanket 16 also dampens vibrations from the exhaustsystem that might otherwise damage the brittle ceramic of the substratebody 10.

In use, the encased brick (or bricks) is mounted in the vehicle exhaustline to receive exhaust gases from the engine and to pass them to thevehicle tail pipe. Exhaust gases 32 enter the front of the gaseousemissions treatment component 10 and treated exhaust gases 34 exit fromits rear. In the course of passing along the cells, the exhaust gasesthe ceramic brick 10 and the catalyst coating is heated to promotetreatment processes where the flowing gases contact the catalyst layer.Especially when the vehicle engine is being run at optimal operatingtemperature and when there is substantial throughput of exhaust gases,such treatment components operate substantially to reduce the presenceof noxious gaseous emissions entering the atmosphere. Such componentshave shortcomings however at start-up when the interior of the brick isat low temperature, during idling during city driving or when waitingfor a coffee at a Tim Hortons drive-through, and between electricdriving periods for hybrid vehicles.

Brick shape, profile and cell densities vary among differentmanufacturers. For example, while most bricks are round, some are oval,square or irregular in cross-sectional shape. Some assemblies havesingle stage bricks that are generally heavily wash-coated with thecatalyst metals, while others may have two or three bricks withdifferent wash-coatings on each brick. Some exhausts have 900, 600 and400 cpsi cell densities used in the full exhaust assembly, while othersuse only 400 cpsi bricks throughout. A close-coupled converter may bemounted up close to the exhaust manifold with a view to reducing theperiod between start-up and light-off temperature. An underfloorconverter can be located further from the engine where it will takerelatively longer to heat up but be relatively larger and used to treatthe majority of gases once the exhaust assembly is up to temperature. Inanother configuration, a component for reducing the period to light-offtemperature and a component to deal with high gas flow after light-offare mounted together in a common casing.

At one or more locations in the assembly, sensors mounted in the exhaustgas flow including within or adjacent the substrate body providefeedback to the engine control system for emission checking and tuningpurposes. Aside from start-up, control of fuel and air input has theobject typically of maintaining a 14.6:1 air:fuel ratio for an optimalcombination of power and cleanliness. A ratio higher than this producesa lean condition—not enough fuel. A lower ratio produces a richcondition—too much fuel. The start-up procedure on some vehicles runsrich for an initial few seconds to get heat into the engine andultimately the catalytic converter. The structures and operating methodsdescribed below for indirectly heating the catalyst layers and theexhaust gases can be used with each of a close-coupled catalyticconverter, an underfloor converter, and a combination of the two.Outputs from the temperature sensors are taken to a controller at whichthe monitored temperature or temperatures are used to control wheninduction heating is switched on and off. Using an appropriate algorithmimplemented at the controller, the monitored temperatures may also beused to control specific effects of the applied heating processes toachieve a particular heating pattern.

As disclosed in U.S. Pat. No. 9,488,085, a gaseous emissions treatmentassembly such as that shown in FIG. 1 is modified as shown in FIGS. 2and 3 to enable induction heating. Induction heating is a process inwhich a metal body is heated by applying a varying electromagnetic fieldso as to change the magnetic field to which the metal body is subject.This, in turn, induces eddy currents within the body, thereby causingresistive heating of the body. In the case of a ferromagnetic metalbody, heat is also generated by a hysteresis effect. When thenon-magnetized ferromagnetic metal is placed into a magnetic field, themetal becomes magnetized with the creation of magnetic domains havingopposite poles. The varying field periodically initiates pole reversalin the magnetic domains, the reversals in response to high frequencyinduction field variation on the order of 1,000s to 1,000,000s cyclesper second (Hz) depending on the material, mass, and shape of theferromagnetic metal body. Magnetic domain polarity is not easilyreversed and the resistance to reversal causes further heat generationin the metal.

As illustrated in FIGS. 2 and 3, surrounding the ceramic substrate body10 is a metal coil 20 and, although not visible in FIG. 2, locatedwithin selected ones of the cells 12 are metal inserts 22 (FIG. 4) suchas wires. By generating a varying electromagnetic field at the coil 20,a chain reaction is initiated, the end result of which is that afterstart-up of a vehicle equipped with an exhaust system embodying theinvention, light-off temperature may be attained more quickly in thepresence of the varying electromagnetic induction field than if therewere no such field. The chain reaction is as follows: the varyingelectromagnetic field induces eddy currents in the metal elements 22;the eddy currents cause heating of the metal elements; heat from themetal elements 22 is transferred to the ceramic substrate body 10; heatfrom the heated substrate body 10 is transferred to exhaust gas as itpasses through the emissions control component; and the heated exhaustgas causes exothermic catalytic reactions to be initiated more quicklyat the walls 14 compared to the period to initiation by exhaust gashaving only heating from operation of the vehicle engine. Conductionfrom the heated metal elements 22 is the primary source of heat transferto the ceramic substrate 10 and therefore to the exhaust gases when theemissions component is in operation. There is also a small amount ofconvective and radiated heat transfer at any small air gaps betweenmetal elements such as wires and the interior surface of the cellswithin which they are contained.

The coil 20 is a wound length of copper tube, although other materialssuch as copper wire or litz wire may be used. Copper tube is preferredbecause it offers high surface area in terms of other dimensions of thecoil; induction being a skin-effect phenomenon, high surface area is ofadvantage in generating the varying field. If litz wire or copper wireis used, an enamel or other coating on the wire is configured not toburn off during sustained high temperature operation of the converter.An air gap between the coil 20 and the nearest inductance metal elements22 prevents significant heat transfer from the metal elements 22 to thecoil 10 which would otherwise increase the coil resistivity and so lowerits efficiency.

A layer 24 of electromagnetic field shielding/concentrating material islocated immediately outside the coil 20 to provide induction shieldingand to reduce induction loss to the metal converter housing. The layer24 also acts to increase inductive coupling to the metal in thesubstrate body 10 to focus heating. The shield/concentrator 24 can bemade from a ferrite or other high-permeability, low-power-loss materialssuch as Giron, MagnetShield, Papershield, Finemet, CobalTex, or othermagnetic shielding material that can be arranged to surround some or allof the windings of the coil 20. In particular, the magnetic shield 24operates as a magnetic flux concentrator, flux intensifier, diverter, orflux controller to contain the magnetic fields within the substratebody. The magnetic shield lowers loss by mitigating undesirable heatingof adjacent conductive materials. Without the magneticshield/concentrator 24, magnetic flux produced by the coil 20 couldspread around the coil 20 and link with the electrically conductivesurroundings such as the metal casing 18 and other surrounding metal inan exhaust system, and/or other components of an internal combustionengine, vehicle, generator or other electrical system or host system,decreasing the life of these components and increasing energy loss. Inaddition, the layer 24 operates to direct or concentrate the magneticfield to the substrate body 10 providing selective or enhanced heatingof a desired region of the substrate body 10, for example, byredirecting magnetic flux that would otherwise travel away from thatdesired region. In particular, the layer 24 operates to concentrate themagnetic flux produced by the coil 20 in the direction of the metalelements 22 in the substrate body 10 for more efficient heating. As anadditional benefit, the magnetic shield can improve the electricalefficiency of the induction coil 20 by increasing power transfer.

The coil is contained in a fiber insulation sheath 26 with the sheathedcoil being encased in a in cast, cured insulation. The sheath functionsboth to stabilize the coil position and to create an air-tight seal toconfine passage of the exhaust gases through the ceramic honeycombsubstrate body 10 where catalytic action takes place. The insulationalso provides a barrier to prevent the induction coil 20 from shortingon the converter can 18 or the ferrite shield 24. The insulation issuitably alumino-silicate mastic. Alternatively, the substrate body canbe wrapped in an alumino-silicate fiber paper. In one manufacturingmethod, the copper coil 20 is wrapped around the substrate body and thenplaced in the casing or can 18. In an alternative manufacturing method,the coil 20 is placed in the can or casing 18 and the substrate body 10is inserted into the coil/can assembly.

A varying electromagnetic induction field is generated at the coil byapplying power from either a DC or AC source. Conventional automobileshave 12 VDC electrical systems. The induction system can operate oneither DC or AC power supply. The induction signal produced can also beeither DC or AC driven. For either DC or AC, this produces a frequencyof 1 to 200 kHz, a RMS voltage of 130 to 200V and amperage of 5 to 8 Ausing 1 kw of power as an example. In one example suitable for roadvehicles, a DC to DC bus converts the vehicle's 12 VDC battery power tothe required DC voltage outlined above. In another example suitable forconventional road vehicles, a DC to AC inverter converts the vehicle's12V DC battery power to the desired AC voltage outlined above. Anotherexample is more suited to hybrid vehicles having both internalcombustion engines and electric motors have on-board batteries rated inthe order of 360V voltage and 50 kW power. In this case, the batterysupply power is higher, but the same basic DC to DC bus or DC to ACinverter electrical configuration can be applied. An insulated gatebipolar transistor (IGBT) or metal-oxide-semiconductor field effecttransistor (MOSFET) high speed switch is used to change the direction ofelectrical flow through the coil. In terms of the effect of a varyingelectromagnetic induction field on metal in the ceramic substrate body,a low switching frequency produces a longer waveform providing goodfield penetration below the surface of the metal element and thereforerelatively uniform heating. However, this is at the sacrifice of hightemperature and rapid heating owing to the lack of switching. Incontrast, a high switching frequency produces a shorter waveform, whichgenerates higher surface temperature at the sacrifice of penetrationdepth. Applied power is limited to avoid the risk of melting the metalelements or having them reach Curie point. A suitable power input to asingle brick coil is of the order of 1.1 kw, although more than 10 kW ispossible.

As previously described, metal inserts 22 made of ferromagnetic or othermetal are located at selected locations of the ceramic substrate body 10as shown in the detail view of FIG. 4.

Field produced by the electromagnetic induction coil can be tuned to themetal load to achieve high efficiency in terms of generating heat andreduced time to light-off temperature. Heating effects can be modifiedby appropriate selection of any or all of (a) the electrical inputwaveform to the coil 20, (b) nature and position of passive flux controlelements such as the shield/concentrator 24, and (c) nature, position,and configuration of the coil 20. In addition, the applied field can bechanged with time so that there is interdependence between the inductionfield/heating pattern and the particular operational phase; for example,pre-start-up, warm-up, highway driving, idling and for hybrids,intermittent change over from internal combustion to electric drive. Inan alternative configuration, more than one coil can be used to obtaindesired induction effects.

The heating pattern can be determined by appropriate location andconfiguration of the metal inserts 22. A suitable metal for the insertedmetal elements is a ferromagnetic metal such as stainless steel grade430 which has high magnetic permeability and corrosion resistance. Lowerpermeability alloys such as 300 or 400 series stainless steels may alsobe used. Alternative metals can be used depending on particularproperties required. For shaping the direction and strength of magneticflux in the substrate, lower magnetic permeability metals or alloys maybe used for the metal elements in the outer cells with relatively highermagnetic permeability metals being used for metal inserts in the innercells. Metals having very high magnetic permeability may also be used.For example, Kanthal iron-chrome-aluminum alloy stock manufactured bySandvik has a relative permeability of 9000 and greater. High relativepermeability can be achieved using stock made of other alloys includingnickel-iron and iron-cobalt alloys.

With cells per square inch (cpsi) in the ceramic substrates being from400 to 900 and higher, the cross sectional area of cells that are, inthe course of production, to receive metal inserts is very small. U.S.patent application Ser. No. 15/486,369 discloses methods for insertingmetal elements such as wires into selected cells of a ceramic substrate.

Referring to FIG. 5, in an alternative method for inserting metal,molten metal is injected into selected cells 22 of the ceramic substrate10. In preparation for manufacture, ceramic substrate 10 is loaded intoa support fixture at an injection station 42 having a chamber 36. Amasking gasket 38 is fixed to one end of the substrate 10 to cover theends of cells 12 which are to remain empty and to expose the ends ofcells 12 into which metal is to be injected. A conveyance subsystem,which may, for example, be any one of a suction, positive displacementand auger drive, conveys the molten metal from a crucible furnace alonga high pressure line 40 to the injection station 42. At the injectionstation, a metered charge 44 of the molten metal is injected into thechamber 36 above a ram 46 and the ram is moved upwardly to drive themetal through the apertures in the masking gasket 38 and along theselected cells 12. Injection orientation is not significant. A top plate48 is configured to allow the escape of air but prevents metal fromexiting from the other ends of the cells 12. The masking gasket 38 andtop plate 48 are made of a metal with higher melting temperature thanthat of the metal being injected; for example, steel fixtures may beused for aluminum injection. These substrate 10, gasket 38 and plate 48are clamped together prior to injection to avoid leakage of molten metalinto non-selected cells 12. Flow of the molten metal is manipulated soas to mitigate back pressure build-up caused as solidification startsand which might otherwise cause changes in the rheology of the moltenmetal, making injection more difficult. Adverse changes in rheology mayresult in breakage of the ceramic and/or freeze-off of the metal charge44 when only partially injected. A pressure of from 100 psi to 300 psiand rapid metal injection effected in a fraction of a second are neededto avoid premature freezing of the molten metal before it reaches itsdesired location. A 4 inch diameter ceramic substrate with 400 cpsi cantypically withstand an axial compressive force of 10 MPa (1450 psi), anda radial compressive force of 2 MPa (290 psi). This is in contrast withan injection pressure greater than 1000 psi for typical commercial metaldie-casting.

Placement of the masking gasket 38 is effected just prior to metalinjection via a vision system and robotic manipulation. The visionsystem identifies the current position and orientation of the substrateand the associated deviation from a prescribed orientation for properinjection. The deviation is converted to a robotic motion to manipulateeither or both of the masking gasket 38 and the substrate 10 beforeclamping and injection. In conventional high pressure injection ofmolten metal parts, the die/mold is of a clam shell form that is rapidlyopened and closed for quick feed rates with the dies being cooled forrapid solidification. Such dies are also normally heavily constructed towithstand high hydraulic pressures. For injecting the ceramic substrate10, the die/mold is the substrate itself and there is no cooling tocontrol temperature or the ability to materially increase the mass ofthe ceramic. In most implementations, cells immediately adjacent a cellinto which metal is injected are empty so the only structural support isthe surrounding ceramic walls. Pressures acting against the delicatecell walls 14 must be kept below a level at which they would be damaged.However, although thin-walled, the nature of the honeycomb ceramic andthe injection pattern contribute to survivability of the substrateduring injection. Thus, a single, large solid part takes a relativelylong time to cool because the surface area to volume ratio is typicallyfrom 1:1 to 10:1. In contrast, the surface area to volume ratio of a 4inch diameter ceramic substrate with 400 cpsi, and one cell in 25occupied by metal is of the order of 100:1. This means that injectedmolten metal cools almost instantly upon injection because of the lowmetal mass and the high surface area of ceramic which allows heat to berapidly conducted from the molten metal into the ceramic. When a rampushes molten metal into a conventional mold, hydraulic pressure isnormally exerted equally in all directions on the mold surface. With theinjection into the ceramic substrate cells, the ram pressure quicklychanges from hydraulic to axially directed pressure as the metalsolidifies. Consequently, the walls of a cell 12 into which molten metalis injected are not significantly stressed and the risk of blowing awall out is minimized. Resistance to compression, which is the strongestin the axial direction orientation of the ceramic substrate 10, isincreased by the addition of the solid metal inserts produced by theinjection. Injections into a cold substrate are generally over the fulllength of the injected cells, because it is difficult effectively tocontrol partial injection in view of the required high injection speed.Following injection, the parts separate with a relatively clean edge. Inthe case for example of aluminum injection with steel tooling,separation is straightforward because aluminum does not stick to steeleven when molten. Ram injection is designed to evacuate all the moltenmetal in the chamber which means that the only metal left in the systemis in the cells of the ceramic and the through-holes in the maskinggasket. This residual metal in the gasket layer is a very small amountof material and is partially or wholly consumed as the injected metalshrinks during solidification. In another embodiment, the ram plate hassmall protrusions that interface with the through holes in the maskinggasket 38. At the end of the injection stroke, the ram plate touches themasking gasket and the protrusions project into the through holes topurge them of residual metal. The fixtures can be coated between cycleswith a die release lubricant.

In a modified process, the ceramic substrate is pre-heated close to, butbelow, the melting temperature of the molten metal. Having the ceramicheated affords more time before solidification of injected metal occurs.This means that injection or dosing of the metal is effected moreslowly, under greater control and at a preferred relatively lowerinjection pressure from 25 psi and 200 psi. Using a heated substratealso minimizes thermal shock experienced by the metal and the ceramicand so limits stress resulting from cooling. Mechanical bonding betweenthe metal and the substrate cell walls is also generally improvedcompared with cold injection. Injection into a pre-heated substrate alsoreduces the effect of metal shrinkage occurring upon solidificationbecause the heated ceramic is larger than at room temperature and soshrinks as it cools. Although there will be some separation because theceramic shrinks less than the contained metal, pre-heating of theceramic reduces the shrinkage difference. Actually, some shrinkagedifferential is desirable, because, at high temperature reached when acomponent is operating to treat hot exhaust gas, the separation providesa buffer between the metal and the ceramic. The buffer is also valuablewhen, in operation, the component is inductively heated because themetal heats up relatively quickly before the ceramic has started toexpand. Rapid cooling that characterizes injection into a cold substratecan cause the perimeter of a metal plug to freeze off quickly resultingin metal shrinkage being predominantly in the middle of the metal. Thiscan lead to defects such as cracks and voids. With a pre-heated ceramicsubstrate, slow cooling results, thereby allowing the perimeter andmiddle to cool together, to shrink at a much closer rate, and so limitdefect formation. As will be described presently, the interior surfacesof the cells 12 are not perfectly smooth and the molten metal conformssomewhat to these surfaces as it solidifies, so providing some level ofmechanical retention of the solidified metal elements 22.

In an alternative process, as illustrated in FIG. 6, a masking gasket 38is applied to the ceramic substrate 10 which is then submerged in a bath50 containing molten metal 52 and lowered to a level at which pressureacting on the surface of the contained metal 52 coupled with surfacetension forces causes the molten metal to enter from the bottom of thecells and to rise to a level in the substrate corresponding to thedesired length of metal insert. Low surface tension and low viscosityare desirable to have liquid rise in a cell. However, the surfacetension of molten metal is high, (about 0.9 Newtons/meter for aluminumat 600° C.), as is its viscosity, (about 3×10⁻³ Pa-s for aluminum at600° C.). Consequently, a vacuum suctioning system may be used to drawthe molten metal through the substrate channels. Vacuum suctioningparameters may be adjusted to place induction heating metal in contactwith the cell walls only where desired; for example, limited to one endregion of the substrate. The whole substrate can have metal in contactor just select passages using a gasket or masking technique. For fullfilling, molten metal is drawn all the way along a channel using highand sustained vacuum. For partially filling, metal is drawn to a desireddistance from the face of the substrate by applying and maintaining alesser vacuum. As indicated previously, selected passages can be fully(blocked) or partially (lined) filled. For blocking, the vacuum ismaintained for an extended period of time sufficient for solidification.Coating the channels requires the release of the vacuum after a certaininterval to allow excess molten metal to drain from the cell. Theinterval is proportional to the desired thickness of the coating with ashorter interval producing a relatively thin coating and a longerinterval producing a relatively thick coating. Thus a combination ofdepth of submersion and level of applied vacuum is used to control theamount of filling in the channels. Reversing the vacuum and injectingair is also implemented if necessary to purge molten metal from thechannels and leave only the coating encompassing a through hole in thechannel. Following application and solidification of the inductionheating metal, as shown in FIG. 7, the substrate 10 is submerged in abath 54 of a catalyst-containing wash-coat 56 which is applied to thewalls of the empty cells and to the selected cells if they are not fullyblocked by induction heating metal. Resulting adhesion forces betweenthe bare ceramic and the inductive heating metal are high. The sequenceof induction metal coating and catalyst wash coating can be reversedwithout any significant effect on performance and integrity.

In another method as illustrated in FIG. 8, metal particles 58 areinjected or pumped into selected cells 12 and the substrate 10 isvibrated 60 at high frequency to cause the particles 58 to fall undergravity and to settle against a bottom plate temporarily placed underthe substrate 10 to block the ends of the selected cells. The particles58 are then heated to the melting or softening point of the metal.Heating to the melting point renders the particles into a fully moltenmass. An additional amount of metal particles must be added tocompensate for reduction in volume caused by collapse of interstitialvoids if the cell is to be filled throughout its length. As in directmolten metal injection, the subsequently melted metal generally conformsto the profile of the inside surfaces of the cell walls resulting insome mechanical retention to keep the inserted metal in place. Meltingonly to the softening point promotes surface melting or wetting butheating is not sufficient to fully melt the particles 58. Consequently,the particles substantially retain their original volume and shape whilebeing physically and electrically linked like a solid. The matrix volumeis retained but with a weight lower than a solid metal plug of the samesize. As the particles 58 collect in a cell 12, vibration amplitude ofthe collected particle decreases and the aggregate density of theaccumulated particles increases. The vibration filling process worksonly with gravity; that is, the particles collect and build upwardlyfrom the bottom end of the selected cells. In a variation, vibration tofluidize particle flow to the substrate and into the cells is attaineddirectly by applying an oscillating electric field to the particles. Oneeffect of filling from a fluidize flow is that the accumulations offluidized particles tend to self-level.

In a variation for cell filling as shown in FIG. 9, air is used tofluidize metal particles to facilitate filling of the cells. Highpressure air 64 is injected into a vessel 66 holding the metal particles68. The pressurized air drives the metal particles down though smallholes 39 in a masking gasket 38. The holes 39 register with the ends ofcells 12 to be filled with metal powder with other parts of the gasketcovering the ends of cells 12 that are to remain empty. The air 64 actsto float and separate the metal particles 68 to establish flow where itwould otherwise be very difficult. Escape of air through the holes 39permits more air to be injected which keeps the metal powder 68 fluid aswell as maintaining an air path through the selected cells. Gradually,the selected cells fill with the metal particles 68 with the aircontinuing to escape via voids between the particles. The pressure ofair pushes the particles down into the selected cells as more metalenters the cells and packs particles already in place against a bottomsupport plate 62. A fine mesh screen 70 that has openings sized smallerthan the smallest particle size allows the air to exit the system butretains all the particles within the selected cells. Air fluidizedparticles flow with the air path which means that the selected cells 12can be filled from either the top or bottom. Filling from the bottomusing an upward flow of air may be supplemented either by lowering thesubstrate into the fluidized particles or raising the fluidized bed upbeyond the bottom of the substrate. Once the selected cells are filledwith powder to a desired level, the metal powder is heated to melt orsoften it as previously described. In an alternative to the use of metalparticles, a length of wire is placed at a desired position in a cellusing for example one of the methods described U.S. patent applicationSer. No. 15/486,369 and then heated to the melting or softening point ofthe metal.

Referring to FIG. 10, in another method for placing induction heatingmetal into selected cells, a ‘green’ slurry 72 containing particles 76of ceramic (alumina) and particles 74 of an induction heating metal iscoated onto the walls 14 of selected cells 12 or onto the walls of allcells of the substrate 10. The induction heating metal 74 may be of fineparticle size on the same order of the size of particles of catalystmetals or may be larger in size provided they are materially smallerthan the cell span so that blockage by a particle is avoided. The slurry72 is prepared by combining water, alumina, powdered metal (eitherinduction metal or a mix of induction metal and catalyst metal) and anoptional binder and the substrate is lowered into the slurry to coat theselected cells. The amount of liquid in the mix (mainly water) is variedto achieve a viscosity low enough that it flows into the cells 12 buthigh enough to leave a coating with a measurable thickness. Vacuumassistance may be used to encourage flow of the slurry into the cells12, the vacuuming also serving to distribute the coating and to keepcell centers clear to avoid blockage owing to surface tension effects.In one process variation, the slurry forms a coating layer on the insideof a cell. If catalyst metal is mixed with the induction metal or isapplied as an overlayer after the induction heating layer is applied,the catalyst metal promotes gaseous emissions treatment within theparticular cell when the component is use in exhaust gas treatment.Induction heating metal particles and catalyst metal particles may bemixed and applied together in a single slurry or they may be mixed andapplied in separate slurries. Metal layering of all cells by inductionheating metal means that, when the component is operated in the courseof gaseous emissions treatment, some level of inductive heating takesplace at every cell. In this case, the inductive metal heating layerresides just below the surface of the catalyst layer resulting, inoperation, in only a short time being needed to heat the catalystwashcoat to the actuation or light-off temperature. In a furthervariation, the induction heating metal completely or substantiallyblocks selected cells. To achieve substantial blockage, layers of slurryare successively applied until the cell is closed or the substrate ispartially or fully submerged in the slurry. In both cases, sufficienttime is allotted for capillary action to draw moisture out of the slurryand so leave a cake or plug within the cell. Secondary curing is used tostabilize the plug. In each of the slurry process variations, the greenslurry coating or plug is fired after placement in order to chemicallyand mechanically bond the induction heating metal layer to thesubstrate. The substrates are previously fully-fired, so only theapplied metal need be cured. The substrates are heated to a temperaturebelow the firing temperature for the substrates and above the maximumin-use application temperature, typically between 800 and 1200° C.While, metal slurry processes are slower than molten metal injection,stress on the substrate is usually lower.

Referring to the detail view of FIG. 11, a characteristic of a plug orlayer of metal that undergoes a molten to solid transition within a cellis that the surface of the solidified metal conforms somewhat to thesurrounding ceramic walls as shown by the tracked surface shape at 80.Because the wall surfaces are not totally smooth and regular, the moltento solid transition provides some degree of retention of the metal plugor layer in the cell. Texturing or roughness in the ceramic surface,whether present as an artefact of normal extrusion or deliberatelyapplied though imposed extrusion conditions and equipment, provides ameasure of mechanical lock at pores and overhangs in the ceramic surfacealthough the metal surface geometry does not conform absolutely to theceramic surface geometry because metal has a high surface tension andthe ceramic is fairly non-wetting. Surface texturing also increases thesurface area of a cell and increases the amount of heat conductionbetween the metal and the ceramic wall compared with perfectly smoothand regular metal and ceramic wall interfaces. Depending on the natureof the ceramic and the metal, there may also be some chemical reactionbetween the two materials if the temperatures are close to or above theceramic sintering temperature or there is a reactive species in themetal alloy that makes a new material at the interface.

However, the metal typically has a coefficient of thermal expansionseveral times that of the ceramic which means that a tight interface cancause damaging stresses in the course of operational temperaturecycling. To combat this to the extent possible, the molten metal/ceramiccombination is put together a high temperature and then cooled. In thiscase, the metal contracts considerably more than the surrounding ceramicbut with a residual imprint of the ceramic surface at the metal surfaceover at least part of the metal surface.

In one example, a combination of a cordierite substrate and injectedaluminum was used. Cordierite has a coefficient of thermal expansion ofabout 2×10{circumflex over ( )}−6/° C. and aluminum has a coefficient ofthermal expansion of about 24×10{circumflex over ( )}−6/° C. This meansthat aluminum has 12× the expansion of cordierite over a giventemperature range. When heated from room temperature to 950° C., thepeak temperature of a gasoline application, cordierite expanded 0.0019inches per inch length of material and aluminum expanded 0.0228 inchesper inch length of material. Consequently, the expanded difference inlength at 950° C. was 0.0209 inches per inch length. For the 0.031 inchdiameter (span) square pin used, the difference was 0.00065 inches(0.0209 inches per inch of length×0.031 inches=0.00065). To attain lowoperational stress at 950° C. coupled with highest possible conformancefor retention purposes between the outer surface of the metal and theinner surface of the cell walls, process conditions were selected toachieve a 0.000325 inches gap between the metal and the cell walls atroom temperature in order for there to be no gap but maximum surfaceretention at the 950° C. application temperature. Ideally, forsubsequent operational purposes, a gap of uniform spacing exists overthe complete metal ceramic interface, this being more readily achievedif the cooling of the ceramic metal combination during manufacture isalso uniform. For example, if in a radial sense there is a variation incooling rate in the metal a shrinkage gap may open up other than at themetal ceramic interface. Also, for ideal operational purposes, it ispreferable that heating of the ceramic metal combination whether by thepassage of exhaust gas or by induction heating should also be uniform sothat the buffer gap between the ceramic and metal uniformly closes asthe vehicular application increases to its operating temperature. Asindicated, wall surface roughness or texturing can provide retention ofclose positioned metal. In one production method, the cells that are toaccommodate induction heating metal in the finished product are duringextrusion deliberately configured to provide non-smooth wall surfaces toaccentuate retention.

Referring to FIG. 12, in another method for placing metal in the ceramicsubstrate, metal in solid form such as wires 82 are pulled through anextrusion die 84 at the time of extruding clay or clay/ceramic mixthrough the die to produce a green extrusion to be dried and fired andcut into lengths to form the ceramic honeycomb bricks. If, during theextrusion, the wires are entrained within cell walls, the methodconnotes a low cpsi compared to current commercial high cpsi honeycombsubstrates because the thin walls of high cpsi substrates offer littleroom for accommodation of metal wire. In a variation, a die is modifiedto so that the wire is pulled along a honeycomb cell site so aseffectively to fill the cell as the cell is formed. Die apertures forthe wires have tight tolerance relative to the wire gauge to ensure thatthe wire does not move from side to side and to prevent the clay orclay/ceramic mix from exiting through the apertures. In both cases,leading ends of the wires are attached to a pull plate which is used toadvance the wires at the same rate as the extrudate. The pull plate incombination with drag from the die is also used to tension the wires soas to hold them on line and equally spaced from neighbouring wires,lateral displacement of the wires being prevented to avoid damage toadjacent cell walls.

Normally, cutting a clay mix extrudate is effected using a thin cuttingwire. The inclusion of induction heating wire in the extrudate makescutting to length difficult. Whether the extrudate is cut into billetsbefore or after firing, the cutting process is slow. If cutting iseffected before firing, care must be taken to avoid damage of thecomposite structure by unwanted vibration of the induction heating wirefrom its locations in the relatively soft green cell walls. If theextrudate is cut after firing, cutting remains somewhat difficult.Ceramics are typically cut with a diamond blade while metals aretypically cut with a ceramic blade. A combination blade that containsboth diamond and ceramic is required to cut through the wire withoutdamaging the ceramic. In an alternative co-extrusion process, finitelengths of wire are pre-cut and pulled through the extruder. Extrusionis complete when the set of short wires for a particular substrate havebeen pulled completely through the die. The wires are released from theother end resulting in a green, honeycomb billet ready for cutting by awire saw at a cross sectional plane not occupied by induction heatingwire. After cutting, the billet is dried and fired.

Referring to FIG. 13, in another method for placing solid metal in aceramic substrate 10, metal powder and green ceramic material—typicallyclay or a particulate ceramic/clay mix—is formed into a paste 88. In themanufacture of the ceramic substrate, the paste is extruded through adie 84 to produce a composite ceramic/clay metal honeycomb. Either orboth of the metal powder content and its distribution are selected tomake the substrate inductively active to enable operational inductionheating. The metal content is on the order of high-10s to low-100s ofgrams for a typical 4 inch diameter by 6 inch long 400 cpsi substrate.Actual metal content depends on how much power the catalytic converteror PDF is to absorb when the component is in use. Many applicationsdemand quick heating or high power which require a relatively high metalcontent. The concentration of metal can be varied along the length ofthe substrate and/or across its span. The density of metal is severaltimes that of the clay or ceramic ingredients in the mix. Water is addedto or removed from the ingredients depending on the powdered metalcontent and its particle size. Metal typically has a lower affinity forwater than clay/ceramic materials so less water is required for the sameparticle size. More water is required if the particle size of thepowdered metal is smaller than that of the powdered clay materials.Water content and particle size are adjusted to produce a desiredrheology; for example, to match current commercially used substrateextrusion processes. The metal/clay extrudate is then dried and fired.The metal is chosen to be stable at the ceramic firing temperature andis therefore a spectator material residing in the ceramic matrix withoutreacting with the ceramic to form radically new products. Incomposition, the matrix is sintered ceramic with trapped individualmetal particles. It is beneficial, although not critical, that the metalcontent consolidates as a result of firing to produce electricalcontinuity in all or part of the metal. The metal typically has athermal expansion several times that of the ceramic meaning that thesubstrate itself expands more than current commercially used substratesthat are devoid of metal. In one form of emissions treatment assembly,to allow a greater dimensional change, a thicker insulation mat ispositioned between the ceramic/metal substrate and a surrounding sheetmetal canister.

In another process embodiment, streams of (a) a metal powder-greenceramic slurry and (b) a green ceramic mix are co-extruded through a dieso that the green ceramic mix forms walls of the honeycomb and themetal-green ceramic slurry eventually forms induction heating elementssited adjacent certain of the honeycomb walls. The metal powder andgreen ceramic slurry is pumped into and through the die during extrusionof the main green clay/ceramic component. A slurry is necessary becausehoneycomb dies used for high cpsi extrusions are so intricate that it isdifficult successfully to co-extrude two high viscosity materials. Thelow viscosity metal-ceramic is pumped into the die at locations suchthat it coats walls of the clay/ceramic cells with a thin layer ofinductive metal-ceramic as the walls are extruded. The thickness of thelayer is not as critical as the concentration of metal in the layer. Forexample, a solid 0.031 inches span wire in a 1 in 9 pattern for a 600cpsi ceramic substrate is equivalent for induction heating purposes tocoating all 9 cells in the array for the same ceramic substrate with ametal layer 0.0009 inches thick (or a layer 0.0018 inches for a layermade from a 50:50 slurry made from metal and non-metallic carrier).

In another method of manufacturing a ceramic substrate, a clay orclay/ceramic mix and/or extrusion method is used which results afterfiring in a ceramic honeycomb substrate with wall surfaces havingsignificant imperfections such as surface pores. An induction heatingmetal is used having a melting point below the firing temperature forthe substrate and above a maximum temperature likely to be experiencedin the intended emissions treatment application. At the low end of therange, the typical maximum temperature of an emissions treatment systemis around 950° C. for gasoline powered engines and around 700° C. fordiesel engines. On the high end of the range, the firing temperature fora cordierite ceramic, for example, is typically around 1300° C. and thefiring temperature for a silicon carbide ceramic is typically around2200° C. The choice of induction heating metal depends on many factors,but a major one is that the minimum service temperature is dictated bythe maximum application temperature and the maximum service temperatureis dictated by the minimum ceramic firing temperature, with some bufferfactored in between those limits. The finished and fired ceramicsubstrate is submerged into a bath of the molten metal with the ceramicsubstrate being optionally pre-heated to avoid freeze-off of the moltenmetal as the substrate is being submerged. Coating of part of a celllength is attained by dipping one end of the substrate or other selectregions of cells. Compressed air or vacuum is used to evacuate excessmolten metal from the cells. Molten metal is absorbed into the pores ofthe ceramic and retained upon cooling. The absorption of metal isdependent on the porosity of the ceramic with more porous ceramicsabsorbing more metal. Metal is also retained on the surface of theceramic and is linked to metal in pores extending below the surface ofthe substrate walls. Multiple coats may be required to produce a desiredthickness. The process produces metal that appears to be a coating, butin fact has good penetration depth.

In another method as illustrated in FIG. 14A, atomized molten metal 90,such as a 400 series stainless steel, is deposited on walls of selectedcells of a ceramic honeycomb 10 by plasma spraying. Metal powder 92 isblown from a spray gun 94 that forces the stream through a flame 96 toliquefy the metal particles which then solidify as they land on thesurfaces of cells 12. The duration and placement of coverage varies thethickness and location of the metal coating. Heat retained in theatomized molten metal 90 is miniscule compared to the mass of theceramic substrate 10. Consequently, molten atoms freeze almost instantlyas they encounter the walls 14 of the substrate. Because of the largedifferential in thermal mass, metals with a higher melting temperaturethan the firing temperature of the ceramic substrate can be used becausethey do not raise the temperature of the ceramic to a critical point.Examples are 430 stainless steel (melting point 1425 degrees C.) andKanthal™ (melting point 1500 degrees C.). Constant bombardment by themolten atoms locally increases the temperature so as to create acontinuous film. In the process, the plasma sprayer 94 is moved relativeto a stationary ceramic substrate 10 or the substrate 10 is movedrelative to a stationary sprayer 94. Coating is based on line of sight,so only short ceramic substrates with large cell spans really lendthemselves to plasma spraying unless an adjunct process is used. In onesuch process, flow of the plasma is assisted by establishing a partialvacuum at the opposite end of the substrate 10 from the nozzle plasmasprayer 94. As the molten spray is generated, the vacuum draws it downthe channels of the ceramic substrate where it interacts with thesurface of the channel. It is difficult to establish a uniform thicknesscoating because even with vacuum assist, the coating is generallythicker near the plasma spray gun than farther from it. In oneembodiment, to render a layer more uniform in thickness, aftervacuum-assisted spraying from one end a cell, the cell is vacuum-assistsprayed from the other end. In a variation shown in FIG. 14B, metal ismetered from a bath of molten metal 96. In another modification, thespray system is mounted on a gimbals by means of which the substrate isradially tilted at progressively changing angles to take advantage ofthe effect of gravity. Thus, spraying straight up or straight down acell causes molten particles to travel in a straight line until theirmomentum dissipates. Spraying on an angle augments the trajectory of theparticle permitting more directionality in depositing the atomized metalon the cell walls.

Referring to FIGS. 15 and 16, in another method of placing metal in aceramic substrate, the metal is applied to selected surfaces on thewalls 14 of a ceramic honeycomb 10 by electrodepositing. Because theceramic substrate is not electrically conductive, wall surfaces arefirst made electrically conductive by immersing the ceramic substrate ina bath containing, for example, molten copper or nickel salts or asolution of such salts. The copper or nickel adheres to the ceramic inthe presence of a catalyst, such as palladium chloride or tin chloride,thereby making the ceramic surface electrically conductive.Alternatively, the surface of the honeycomb is painted with metal paint.For specialist applications where high conductivity and corrosionresistance are required, more expensive materials such as any of gold,silver or palladium are deposited to provide the bonding layer. Once theinitial metal layer is deposited or painted, the substrate is immersedin an electro-chemical bath 98 containing an electrolyte, such as asolution of common salts of copper, silver, chromium, nickel or iron.The ceramic substrate functions as an electrode for subsequentelectrodeposition with the other electrode being a sacrificial electrodesuch as a rod 100 made of the metal to be deposited. A hanger wireattached in a cell of the substrate functions to spread charge to theentire substrate. In the case of stainless steel, an electrolytesolution containing Fe(II), Ni(II) and Cr(III) is made, plating beingtypically one metal at a time layer by layer to combine these three maincomponents into a single composite layer. The number and duration ofdeposition baths in the process determines the thickness ofelectrodeposited metal. As previously indicated, in the case ofstainless steel, several different metals are depositing atsubstantially the same time. Layering of different metals may bedesirable for corrosion resistance of lesser metals similar to achroming process. In one example, corrosion resistant chrome is an outerlayer that coats and protects an iron layer having good magneticpermeability. In another example, the cells and the end faces of thesubstrate are coated but the outer surface is covered by a removabletape or wax to block deposition of the initial bonding layer so that nometal is plated on the outer surface in subsequent steps when depositingon the substrate end and interior. The ceramic substrate 10 has acomplex geometry and therefore cannot readily be coated in a turbulentdeposition bath generally used for simpler geometries. In normalcircumstances, turbulence keeps the concentration of metal and saltuniform and replenishes the concentration of metal near the surfacewhere the deposition reaction takes place as indicated in FIG. 16. Thisprocess does not work where channels are very small in cross sectionalarea and so do not permit through flow due to high friction.Consequently, only liquid that gets into the channels reacts, thisreaction coming to an end once the metal is exhausted if it is notreplenished. In one embodiment, a forced flow is used to circulate theelectrolyte through the channels during plating with an anchoringarrangement being used to hold the substrate in place as the bathsolution is pumped through the cells. This ensures that fresh, highmetal concentration liquid is always flowing in close proximity to thesurface of the channels.

As is known in the art, the electrolysis bath has two electrodes, onecharged positively or negatively depending on the metal ions created andthe other being of opposite charge. The ceramic substrate with itsinitial metal coating is charged with the opposite charge of the metalion in order that the metal ion is attracted to the surface fordeposition. A sacrificial electrode 102 oppositely charged to theceramic metal coating attracts the non-metal ion. Metal in theelectrolyte solution comes out of solution when an electricaldifferential is produced on the surface of the substrate. Thisdifferential breaks bonds within the solution allowing the metal portionof the molecule to become solid as it deposits on the metalized ceramic,the active zone for deposition being very close to the substratesurface. The electrolyte in the bath is constantly regenerated to returnhigh concentration solution to the deposition zone. A very low viscositysolution is used in order that it readily flows through the narrowsubstrate channels, so allowing metal to be deposited on all surfaces ofthe ceramic. The number of dipping stages and the deposition time forcoating govern the thickness of the metal coating. Once coated, thesubstrate is washed to remove any remaining unreacted electrolytesolution. The coated substrate must them be dried before catalystwashcoating. Although the exemplary metals mentioned previously areparticularly suitable for electro-deposition, some non-metal conductorssuch as graphite can also be used and offer the advantages of anelectrically conductive non-metal.

Steel, iron, copper, aluminum, among others, and their alloys are allsuitable candidate metals for insertion into cells using one or more ofthe techniques described herein. These metals vary by magneticpermeability, melting temperature and other properties so that thechoice of metal depends on the application parameters. For example, ironhas relatively high magnetic permeability but little corrosionresistance while aluminum has relatively low magnetic permeability butgood corrosion resistance. For use with cordierite ceramics particularlysuitable for diesel applications, a metal with a lower meltingtemperature such as iron or copper may be suitable. For silicon carbideceramics, a metal such as 430 stainless steel with a higher meltingtemperature is more suitable. 430 stainless steel, which has highmagnetic permeability and corrosion resistance, is a preferred metalused in the metal wire placement method of U.S. patent application Ser.No. 14/452,800 mentioned previously, but is difficult to use with someof the metal placement techniques described above. For high temperaturegasoline applications, cordierite substrates are often used. In thesecases, copper and aluminum are preferred for processes requiring moltenmetal because the melting temperatures of iron and its alloys (such asstainless steels) generally exceed the cordierite firing temperature

In most of the metal insertion techniques disclosed herein, a maskinggasket is used to block the entrance of cells that are not selected sothat they remain empty the masking gasket having openings at theentrance of cells into which metal is to be placed. In other techniques,cells can be injected individually with no masking gasket using a smallinjection tip at the end of a robotic arm for precise placement. Theprocess is more time consuming but generally gentler on the delicatewalls of the ceramic substrate.

In many of the metal insertion techniques disclosed herein, the metalmust be heated to melting. This is typically done by one of oven (orfurnace) heating, by inductive heating or by electric arc heating. Ovenheating is the slowest of the heating processes because the relativelymassive ceramic component is heated to the melting temperature of themetal. The metal used must have a melting point below the sinteringtemperature of both the ceramic and any catalyst washcoat previouslyapplied to cell walls. Induction heating or electric arc heating areused where it is desired to focus heating at the metal and a part of thesurrounding ceramic. Induction directly heats the metal until it meltsin the cell. A high power induction supply on the order of 10s to 100sof kilowatts rapidly melts the small masses of metal within eachsubstrate. In one implementation, the substrate is placed inside aninduction coil that is itself contained within a gasket fixture so thatplacement and melting is effected in a combined process. Alternatively,induction heating is performed as a secondary process. Electric arcingpasses high current at high voltage through the metal which melts owingto the resistive properties of the metal. The arc is produced by placingan electrode in close proximity to the metal to be melted so that thepotential arcs from the electrode through the metal. One electrode isplaced at the front face (possibly the front of a gasket layer) and oneelectrode is placed at the back face of the ceramic (bottom support) ina one-step process, or there could be many more electrodes in asecondary step. The ceramic is unaffected other than indirectly heatingup due to the adjacent hot metal.

In the specification, the terms “cell” and “passage” are usedinterchangeably in relation to the described and claimed manufacturingprocesses although generally passages characterize catalytic convertersand cells characterize particulate filters (PFs). In most catalyticconverters, passages are through channels allowing for generallyunimpeded flow of emissions gas past hot catalyst coating the passagewalls. In particulate filters, a checkerboard subset of cells have theirfront ends plugged, a ‘reverse’ checkerboard subset of cells have theirback ends plugged, and gaseous emissions are treated by being driventhough porous walls of the honeycomb structure from cells of the firstsubset into cells of the reverse subset. However some PFs also havecatalyst coating the passage walls.

In this specification and claims, the terms “melting” and “softening” ofmetal are used interchangeably in relation to the described and claimedmanufacturing processes. Heating to the melting point renders theparticles into a fully molten mass. Melting to the softening pointpromotes surface melting or wetting but heating is not sufficient tofully melt the particles.

In this specification, the use of the terms “ceramic mix”, “greenceramic”, “clay” and similar materials and combinations thereof inrelation to the extrusion of material as a precursor of a ceramicsubstrate for use in a gaseous emissions treatment component is intendedto mean any material suitable for making such a substrate used incommercial processes for manufacturing the same.

The invention claimed is:
 1. A method of making a gaseous emissionstreatment component, comprising extruding green ceramic mix through adie to form an extrusion having a honeycomb substrate having a pluralityof elongate cells extending along the extrusion, the cells bounded bywalls dividing adjacent cells from one another, cutting off a length ofthe extrusion, placing molten metal for use in induction heating of thecomponent in at least a part of at least some of the cells in saidlength, and solidifying the molten metal by cooling, wherein saidcooling acts to cool and solidify the molten metal to cause firstshrinkage of the metal and acts to cool the substrate to cause secondshrinkage of the substrate less than the first shrinkage, whereby atsolidification of the molten metal, a space is established at at leastsome of an interface between the solidified metal and adjacent walls ofsaid at least some of the cells.
 2. The method of claim 1, wherein metalis initially introduced in solid form into said at least some of thecells and the introduced metal is heated to melt the introduced metalwhereby it becomes the placed molten metal.
 3. The method of claim 2,wherein the introduced metal in solid form is particulate metal.
 4. Themethod of claim 2, wherein the introduced metal in solid form is a metalwire.
 5. The method of claim 1, further comprising firing the length ofhoneycomb substrate before the molten metal is placed.
 6. The method ofclaim 5, wherein the molten metal is injected at high pressure into saidat least some of the cells.
 7. The method of claim 1, further comprisingheating the length of honeycomb substrate prior to placing the moltenmetal in said at least a part of said at least some of the cells.
 8. Themethod of claim 1, wherein the metal of the solidified metal, a materialof the substrate and dimensions of the at least some of the cells areselected such that when the component is being used in emissionstreatment and operating temperature of the component increases from anexpected lowest temperature operation to an expected highest temperatureoperation, differential expansion between the solidified metal and thesubstrate does not fully close said space.
 9. The method of claim 1,further comprising texturing surfaces of the walls of said at least someof the cells during formation of the extrusion.
 10. The method of claim1, wherein a catalyst metal washcoat is applied to walls of open cellsof the substrate after placing said molten metal in said at least someof the cells.